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Download ENGR-101 Week 02: Shutter Speed Measurement
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ENGR-101 Week 02: Shutter Speed Measurement Today’s Agenda 11:00 Role Call Welcoming Remarks Fun Motivation (Related YouTube Video) 11:15 Experiment 1: Extract camera flash circuit board 11:35 Experiment 2: Oscilloscope and FG setup: burst and trigger 11:55 Experiment 3: Camera flash circuit board installation 12:15 Experiment 4: Reading measurements (with cursors) 12:35 Discussion Points 13:00 Adjourn Generation Gap: Class of 198X vs. Class of 2015+ Terabyte World Atari 400 (16K) – IBM XT (1 MB) Class of 1980x Megabyte Generation Pentium 3 (40 MB) – Multicore (GB) Class of 2015+ Gigabyte Generation Worldwide Optical Content Worldwide Printed Content US Broadcast Media Worldwide Film Content Internet Worldwide Magnetic Content World Telephone Calls Electronic Flow of New Info Giga = 10^6 Tera = 10^12 103 TB 1,633 TB 14,893 TB 420,254 TB 532,897 TB 4,999,230 TB 17,200,000 TB 17, 903, 340 TB Peta = 10^15 Source: Hans Moravec “When Will Computer Hardware Match the Human Brain”, 1997 Biological evolution and human technology both show continual acceleration. The time between events continues to decrease; 2B years from the origin of life to cells and 14 years between the PC and World Wide Web. • 2014: Getting Lost • 2019: Libraries • 2020: Copyright • 2030: Keys • 2033: Coins • 2036: IC cars • 2050+: Ugliness, Nation States, Death Source: “What’s Next” and the “Future Exploration Network” Erosion of Boundaries in the Information Age • Between products and services: think cell phones • Between producers and users: think social media • Between IT, comm, media, consumer electronics: think Amazon • Between IT and non-IT industries: think Walmart • Between academia, industry, disciplines, theory, applied research 1895: “Heavier than air flying machines are impossible”, Lord Kelvin 48 years 1943: “I think there’s a world market for maybe 5 computers”, Thomas Watson 34 years 1977: “There is no reason why anyone should have a PC in their home”, Ken Olsen 4 years 1981: “640K ought to be enough for anyone”, Bill Gates What can we expect in the next 10000 years? 2 Motivation for Today’s Lab • Bring camera: A disposable camera will be disassembled • Search and read about disposable cameras • http://www.ehow.com/how-does_5031419_disposable-cameras-made.html • http://www.youtube.com/watch?v=emjm-HJAsME&feature=related • Search how camera flashes work • http://electronics.howstuffworks.com/camera-flash1.htm • What are coil guns and tasers? • http://www.youtube.com/watch?v=epaMq1vee_c • What is a film ASA rating and how does this relate to shutter speed? • http://en.wikipedia.org/wiki/Film_speed • Roughly calculate the shutter speed needed for a disposable camera http://www.youtube.com/watch?v=epaMq1vee_c Experiment 1: Extract camera flash circuit board Goal: Dissect disposable camera to extract flash circuit Step 1: • Remove battery • Pry apart front and back sides of casing • Remove film • Pry apart flash circuit board assembly Photograph each stage of disassembly ENGR Website: http://core.coe.drexel.edu/node/283 Extra: http://www.youtube.com/watch?v=emjm-HJAsME Lab Notebook: 1-A: Explain how the shutter mechanism works (in your own words/sketches) - What causes the film advance after the capture button is pressed? - What prevents a double-exposure of the film? - How does the shutter mechanism operate? - How does the flash circuit physically operate? 1-B: Include photos at each stage of the disassembly Experiment 2: Oscilloscope and FG setup: burst and trigger Goal: Calibrate instrumentation in order to measure flash Step 1: • Generate square wave at 100 Hz, 5 VPP, 2.5 VDC offset, 5 ms pulse width • Attach function generator to Channel 2Y on oscilloscope • Push Wave Gen • On oscilloscope, press “Autoscale” Step 1 Step 2: Step 2 • On oscilloscope, press the “1” button (directly above input connector) • Set trigger level to 4.0 VDC Step 3: • Press Wave Gen • Set frequency to pulse of 1 Hz Step 4: • On oscilloscope’s Trigger section: Mode – Normal. Experiment 3: Camera flash circuit board installation Step 1: • Scope Channel 1X: camera flash sensor • Scope Channel 2Y: camera shutter sensor • Scope or PC USB: camera USB connector Step 2: • Re-install battery • Fit camera flash circuit board on the measurement board Step 3: • Push the camera flash circuit board button • If necessary adjust Time/Div and Delay setting to get following display Experiment 4: Reading measurements (with cursors) Goal: Use voltage and time cursors to measure flash times Step 1: • Select Cursor. Set Cursor Mode to Manual • Rotate knob to align cursors. Step 2: • Top wave: Flash Pulse Width (time flash remains lit) • Adjust voltage cursors to measure max voltage difference (delta VF) • Position V2 cursor at 0.5*delta VF • Position time cursor T1 at start voltage step • Position time cursor T2 at time where V2 intersects flash signal delta VF Start of Voltage Step: T1 0.5 delta VF T2: Time V2 hits 0.5 delta VF Record Delta T = T2 – T1. This is called the Flash Pulse Width Step 3: • Bottom wave: Shutter Pulse Width (time shutter remains open) • Adjust voltage cursors to measure max voltage difference (delta VS) • Position V2 cursor at 0.5*delta VS • Position time cursor T1 on the rising part of shutter signal (V2) • Position time cursor T2 on the falling part of shutter speed (V2) delta VS Rise point for V2 0.5 delta VS T1 T2 Fall point for V2 Record Delta T = T2 – T1. This is called the Shutter Pulse Width Step 4: • Leading Edge Offset (time between shutter-opening and flash-on) • Place V1 cursor at 0.5 * delta VS for bottom wave (shutter signal) • Place V2 cursor at 0.5* delta VF for top wave (shutter signal) • Place T1 at V1 (rising) intersection • Place T2 at V2 (rising) intersection V2: 0.5 delta VF V1: 0.5 delta VS T1 T2 Record Delta T = T2 – T1. This is called the Leading Edge Offset Step 5: • Trailing Edge Offset (time between flash-off and shutter-close) • Place V1 cursor at 0.5 * delta VS for bottom wave (shutter signal) • Place V2 cursor at 0.5* delta VF for top wave (flash signal) • Place T1 at V1 (falling) intersection • Place T2 at V2 (falling) intersection V2: 0.5 delta VF V1: 0.5 delta VS T2 T1 Record Delta T = T2 – T1. This is called the Trailing Edge Offset Lab Notebook: We want 2 more trials of time data. Repeat Experiment 3 and 4 In your notebook, complete the table below with your values Trial 1 2 3 Avg. Flash Pulse Width (ms) Shutter Pulse Width (ms) Leading Edge Offset (ms) Trailing Edge Offset (ms) Discussion Points Take Home Points: • Disposable camera has fixed features e.g. fixed shutter time • Changes in shutter time will change photo’s brightness • Future labs aim to physically modify the plastic shutter • These modifications will change shutter times and hence photos Source: http://www.increa.com/reverse/dc/ Film ASA (or iSO) Ratings e.g. ISO 100, ISO 800 • Low numbers: slower film = needs more light = longer exposures (slow shutter) • High numbers: faster films = needs less light = shorter exposure (fast shutter) • Slow film = sharper, detailed photos • Fast film = higher contrast and grainy photos Next Time: Week 03 – Intro to Shutter Modification • Bring camera: A disposable camera will be disassembled • Search and read about disposable cameras • http://www.ehow.com/how-does_5031419_disposable-cameras-made.html • http://www.youtube.com/watch?v=emjm-HJAsME&feature=related • Search how camera flashes work • http://electronics.howstuffworks.com/camera-flash1.htm • What are coil guns and tasers? • http://www.youtube.com/watch?v=epaMq1vee_c • What is a film ASA rating and how does this relate to shutter speed? • http://en.wikipedia.org/wiki/Film_speed • Roughly calculate the shutter speed needed for a disposable camera
